Abstract Detail

Ecophysiology

Stanfield, Ryan [1], Bartlett, Megan [2], Forrestel, Beth [2], Elmendorf, Kayla [2].

Linking phloem and xylem traits in 18 different grapevine cultivars with sugar accumulation in berries.

Grapevines (Vitis vinifera) are perennial woody vines with agricultural applications in winemaking and food production. In support of the berry, the xylem and phloem tissues send water and sugars necessary to support berry cell expansion and to maintain cellular turgor as well as metabolism of the organ. Fluid flow through the cylindrical xylem vessels or phloem sieve tubes follow Poiseuille’s law, where increases in cross-sectional radius of conduits increases their conductance to the fourth power. The hypothesis of the current work was that grapevine cultivars vary in their phloem/xylem cross sectional areas and that these differences alter the rate of sugar accumulation in the berries. We took physiological measurements of photosynthesis, leaf water potential and the accumulation of sugars within berries during the summer of 2020. We also collected leaf and berry organ samples (pedicels) in September 2020; these samples were measured from 18 different grapevine varieties taken from a common vineyard at UC Davis. We found that pedicel (stalk connecting grape to stem) phloem area was a significant predictor of the rate of sugar accumulation (Brix total) in the grape berry. We also found that cultivars that are predominantly planted in “warm climates” (17 - 19⁰ C) had significantly larger xylem and phloem areas within petioles and pedicels in comparison to cultivars that are predominately grown in “hot climates” (>19⁰ C). Further, phloem pedicel sieve plate porosity was significantly lower in the grape cultivars from “temperate climates” (15 – 17 ⁰ C). Overall, red grapes had higher rates of sugar accumulation than white grape producing varieties, and this was associated with the white grapes having higher pedicel sieve tube resistances than their red grape counterparts. Last, xylem areas in the leaf mid vein and petiole were significant predictors of leaf water potentials, with larger xylem areas supporting less water stressed leaves. Overall, this work showed that vascular traits and physiological measurements corresponded most when comparisons were made in the same organ. In addition, our common garden experimental design showed that cultivars which are predominately grown in warm environments possess vascular anatomies which result in higher overall conductivities in the xylem and phloem. This leads to the hypothesis that these cultivars are anatomically adapted to their selected environment, which influences their ability to cope with drought and accumulate sugar in their berries.

1 - University Of California, Davis, Department Of Viticulture And Enology, Robert Mondavi Institute, North Building, Davis, CA, 95616, United States
2 - University Of California, Davis, Department Of Viticulture And Enology, Robert Mondavi Institute, North Building, Davis, CA, 95616, USA

Keywords:
Phloem
xylem
Brix
Sugar Accumulation
Grapevine
Anatomy
ecophysiology
microscopy.

Presentation Type: Poster
Number: PPE003
Abstract ID:874
Candidate for Awards:None